The long-term goal of this project is to elucidate the cellular, molecular, and biochemical mechanisms regulating the proliferation and motility of vascular smooth muscle cells (VSMC). VSMC hyperproliferation is a key early event in the pathogenesis of arteriosclerosis, and is the major cause of the high failure rate (restenosis) of many vascular surgical procedures. A hallmark of restenosis is intimal SMC hyperplasia during the first few weeks following surgery. Clearly, a detailed understanding of the mechanisms and molecules that regulate VSMC mitogenesis and migration will provide a therapeutic rationale for controlling VSMC hyperplasia following vascular surgery, and may provide important insights into the pathophysiologic basis for atherogenesis. Our laboratory has provided strong evidence that CCN5, a heparin-induced growth arrest-specific gene, inhibits proliferation and motility in cultured VSMC. Based on this evidence the following hypothesis will be tested: CCN5 is an autocrine regulator of VSMC proliferation and motility in culture and in vivo, and exerts it anti-proliferative and anti-motility effects, at least in part, through regulation of extracellular matrix synthesis and composition. To test this hypothesis, we will: 1) Continue our functional analysis of CCN5 on proliferation, motility, and extracellular matrix in SMC cultured from normal and injured arteries, using adenovirus vectors, recombinant CCN5, small inhibitory RNAs and anti-sense mRNA approaches, 2) Examine the physiologic and developmental functions of CCN5 in knock-out and transgenic mice, with particular attention to cardiovascular defects. In situ hybridization and immunohistochemistry will be employed to determine the spatial and temporal expression pattern of CCN5 mRNA and protein in developing embryos of wild-type, CCN5 heterozygotes and homozygotes. Functional analysis of VSMC cultured from the arteries of genetically altered mice that over- or under-express CCN5 will be carried out; and 3) Characterize the role of CCN5 in both mouse and rat models for vascular injury. We will determine if CCN5 gene or protein therapy might be a useful approach for suppressing restenosis in both the mouse wire-injury and rat balloon angioplasty model systems. The experiments proposed in this application should provide novel insights into VSMC pathophysiology.